This invention relates to lighting fixtures, and more particularly to fluorescent lampholder fittings which are adapted to screw into portable lamps and lighting fixtures. Fluorescent lampholder fittings are presently known which screw into various lamp sockets and provide improved illumination with significant reduction in energy consumption.
The most common units on the market at present are single-lamp, single-level devices, or are two-lamps single-level units designed to replace incandescent light bulbs in portable lamps. Since most portable lamps manufactured at present are fitted with three-way lampholders (commonly called sockets), the consumer finds a loss in function if the three-way light bulb is replaced with a fluorescent converter known as a lampholder fitting. In nearly every case the fluorescent lampholder fitting is fitted with circline lamps of either 15 watts or 22 watts, with the greatest use of the 22 watt due to its lumen output being approximately equal to a 75 watt incandescent bulb. Since three-way incandescent bulbs are normally 100 watt or 150 watt devices, lumen equivalence can only be achieved with two fluorescent lamps. Although a two level device may be built using one or two lamps at a time, the three-way performance is still not achieved.
It is known that a fluorescent lamp can be overdriven by supplying higher than rated current, with only a nominal loss is service life. The inventor has constructed units with true three-way function by using a three-way screw base, a first ballast that operates a single lamp with reliable starting at approximately 700 lumens (50 watt incandescent equivalent), a second ballast that operates the lamp at 1200 lumens (more than a 75 watt bulb), and both ballasts in parallel that operate the lamp at 2000 lumens (more than 100 watt incandescent equivalent), and which will function in three-way mode in a standard lamp socket with three-way switch.